The invention concerns refrigeration or heating, ventilation, and air conditioning (“HVAC”) compressor units of the hermetically sealed type wherein the compressor housing or “shell” encloses the compressor, its drive motor and associated components. The compressor housing typically includes upper and lower cup shaped sections, which, after the compressor, motor, and associated components are mounted therein, are secured together, e.g., by welding along the peripheral mating joint formed by the mated contiguous open end portions of the shell sections.
It is customary in the design and manufacture of such compressors to dimension and configure the shell sections to adequately accommodate, spacewise, the compressor, its motor, and the various auxiliary components, such as, a motor mounting, a suction feed system, a discharge loop, a discharge muffler, and the like. Such design considerations are important, however, other design needs such as diminishing the inherent property of the shell to transmit objectionable noise at objectionable frequencies should be considered and are often compromised by paramount space considerations such as the dimensions and configuration of the refrigeration or air conditioning system housing or cabinet into which the compressor unit must precisely fit.
Objectionable noise is transmitted by the shell and originates or propagates therein either by the mechanical elements of the compressor such as the suction and discharge valves, or by the compression of the refrigerant therein, e.g., pulsations within the suction or discharge system. In this regard, it is recognized by those skilled in the art that the source of the noise, its mode of propagation within the shell, and its manner of transmission by the shell to the human ear are all extremely difficult to understand and predict, and of course, to control.
One of the key components for the operation of the compressor is the oil that is used for the lubrication of the mechanical components of the compressor. The oil to be used in the compressor collects in the oil sump at the base of the lower section of the compressor housing and is pumped or drawn into the moving compressor components from the sump.
Normal operation of the compressor also involves pumping refrigerant though the compressor. Such refrigerant is ideally maintained in gaseous form during its time within the compressor. However, some of the refrigerant may condense and drain into the oil sump. Such condensation can cause dilution of the oil in the oil sump, which hinders the ability of the oil to lubricate the mechanical components of the compressor. It is desirable to have no refrigerant in the oil within the oil sump.
Typically, the oil sump is heated with a heater assembly in order to evaporate any refrigerant condensate that accumulates in the oil sump. The heater assembly is normally positioned in a heater well that is located in the compressor housing near the oil sump. However, because of compressor design considerations the heater well is positioned perpendicularly to, and within, the generally cylindrical side of the compressor. Such a configuration means that the heater well is not always substantially submerged within the oil. At best, the well is only partially submerged into the oil of the oil sump, with the heater well mounted directly on the side of the substantially cylindrical compressor housing. In addition to failing to efficiently transfer heat from the heater to the oil, such a heater well configuration causes a significant amount of sound and other vibrations created by the operation of the compressor to be projected out into the environment.
In addition, the patent literature shows many variations of compressor unit shell heating assembly configurations, including U.S. Pat. Nos. 5,194,717; 5,252,036; and 4,755,657, which attempt to address these existing problems. These heating assemblies are directed toward heating elements that are mounted on the exterior wall of the crankcase and are not designed to function within a heater well element.
What is required is a crankcase heater assembly that causes less noise and vibration from the operation from the compressor to be projected out into the environment to reduce the volume of the sound and intensity of the vibration caused by normal compressor operation and to more efficiently transfer heat from the heating element to the oil in order to more quickly vaporize coolant.